CN115840232A - Drift error correction method for satellite laser ranging - Google Patents
Drift error correction method for satellite laser ranging Download PDFInfo
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Abstract
The invention relates to the field of electric digital data processing, in particular to a drift error correction method for satellite laser ranging. The method comprises the steps of obtaining satellite ranging data and ground target measuring data; performing signal recognition on the ground target measurement data, and calculating the ground target average echo photon number and the corresponding ground target drift error according to the ground target signal recognition result; adding the ground target drift error obtained by calculation into the satellite ranging data, performing signal identification on the satellite ranging data, and calculating the average echo photon number of the satellite and the corresponding satellite drift error according to the satellite signal identification result; and adding the ground target drift error and the satellite drift error obtained by calculation into a result obtained by resolving after signal identification to obtain a corrected result. The satellite laser ranging data is processed by the method, so that the quality of the ranging data can be improved.
Description
Technical Field
The invention relates to the field of electric digital data processing, in particular to a drift error correction method for high-precision satellite laser ranging.
Background
Satellite Laser Ranging (SLR) is a technique for measuring the distance between an observation station and a Satellite by accurately measuring the round-trip time interval of a Laser pulse transmitted from a ground observation station to the Satellite, and the Ranging accuracy can reach the centimeter level. The main scientific applications of SLR are: precisely determining satellite orbits, precisely measuring earth rotation parameters, precisely establishing an earth reference system and the like. These scientific applications have also driven the development of SLR techniques to obtain high quality, high accuracy data.
At present, most laser ranging stations at home and abroad adopt a Single Photon Avalanche Diode (SPAD) as a detector. The SPAD has high quantum efficiency, quick time response and high sensitivity, can detect laser pulse echoes with single photon magnitude at least, is very suitable for the SLR with weak echoes but high-precision data acquisition, and is widely applied to the SLR system. When the SPAD works, the detection of the SPAD is affected by the size of the echo energy, which is particularly indicated in that the detection results of the echo signals with different energies are distributed differently, and errors are generated. This Error is called the drift Error (Walk Error). The detection characteristic has an influence on the system delay calibration process of the SLR system. Calibration of the system delay of SLR systems typically employs earth-target measurement. When performing earth-target measurements, the laser energy is usually artificially attenuated in order to match the magnitude of the earth-target echo signal energy with the magnitude of the satellite echo signal energy, thereby reducing drift errors. However, since the laser energy cannot be finely controlled, the drift error still exists in the laser ranging.
In actual ranging, for a target located at a specific position, echo energy fluctuates due to human factors or environmental factors, and usually, a distance value corresponding to a distribution of measurement data fluctuates accordingly. Such fluctuation of the measured distance value may degrade the quality of the ranging data and reduce the ranging accuracy to some extent if it cannot be handled well. To solve the problem, scientific researchers at home and abroad have made many researches. At present, domestic and foreign researches mainly aim at laser radars to analyze the reasons of drift errors, and provide a method for inhibiting the drift errors from a detection model of a single-photon detector and laser energy.
Nowadays, the precision of satellite laser ranging is approaching to millimeter level, the influence of drift error on ranging is not negligible, and the drift error also needs to be corrected in the field of laser ranging.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a drift error correction method for satellite laser ranging. The invention can effectively correct the drift error in the satellite laser ranging data, thereby improving the data quality and the ranging precision.
In order to achieve the above purpose, the embodiment of the present invention provides the following technical solutions:
in a first aspect, in an embodiment provided by the present invention, a drift error correction method for satellite laser ranging is provided, where drift error is corrected by combining measured data with a theoretical model, and the method includes the following steps:
acquiring satellite ranging data and ground target measurement data;
performing signal recognition on the ground target measurement data, and calculating the ground target average echo photon number and the corresponding ground target drift error according to the ground target signal recognition result;
adding the ground target drift error obtained by calculation into the satellite ranging data, performing signal identification on the satellite ranging data, and calculating the average echo photon number of the satellite and the corresponding satellite drift error according to the satellite signal identification result;
and adding the ground target drift error and the satellite drift error obtained by calculation into a result obtained by resolving after signal identification to obtain a corrected result.
As a further aspect of the present invention, the method for performing signal recognition on the ground target measurement data and calculating the ground target average echo photon number and the corresponding ground target drift error according to the ground target signal recognition result includes:
performing signal identification on the ground target measurement data, and calculating ground target system delay by combining a nominal value;
counting the number of signal photons and the number of noise photons before the arrival of the signal, and calculating the noise triggering probability and the signal detection probability by combining the measurement time so as to calculate the signal triggering probability;
and calculating the average echo photon number of the ground target and the corresponding ground target drift error according to the signal triggering probability.
As a further aspect of the present invention, the signal identification of the satellite ranging data, and the calculation of the average number of echo photons of the satellite and the corresponding satellite drift error according to the satellite signal identification result include:
performing signal identification on satellite ranging data, and counting the number of signal photons and the number of noise photons before the arrival of a signal;
and calculating the noise triggering probability and the signal detection probability according to the measurement time, further calculating to obtain the signal triggering probability, and calculating the average echo photon number of the satellite and the corresponding satellite drift error according to the signal triggering probability.
As a further aspect of the present invention, in the method for correcting drift error in satellite laser ranging, the method for calculating drift error includes:
set the actual distance value of the target to
Drift error->
Comprises the following steps:
in the formula (I), the compound is shown in the specification,
is the laser flight distance.
As a further aspect of the invention, the laser flight distance
The calculation formula of (c) is:
in the formula (I), the compound is shown in the specification,
for the length of the time period during which the signal echo lasts>
Is the probability of detection of the signal within the time period,
the distance value corresponding to each detection probability in the time period.
As a further aspect of the present invention, the method for correcting the drift error of the satellite laser ranging further includes:
calculating a drift error model based on a detection probability model of the single photon detection system,
resolving laser flight distance based on detection probability
Based on the laser flight distance->
And calculating a weighted average value as a detection probability resolving distance value.
As a further aspect of the present invention, in the drift error correction method for satellite laser ranging, the correction result of the satellite ranging data
Comprises the following steps:
wherein the content of the first and second substances,
for the satellite ranging result, is>
Based on the result of the distance measurement of the ground target>
Value for ground target, and->
For a drift error corresponding to the number of photons, <' >>
Is the number of satellite echo photons, <' > is>
Is the number of ground target echo photons.
As a further scheme of the invention, the detection probability comprises the average echo photon number when being calculated, the detection probability is obtained by counting the actually measured data result, and then the average photon number is calculated according to the detection probability; wherein the detection probability obeys Poisson distribution when the average echo photon number is
When the detector detects >>
The probability of an individual photoelectron is:
working in a geiger mode with a range gate, a range gate time is divided into three time periods: before the arrival of the echo signal, within the duration of the echo signal and after the echo signal is finished; in the first period of time and the third period of time, only noise photons enter the detector, and in the second period of time, signal photons and noise photons jointly enter the detector.
As a further aspect of the present invention, in the first period of time, the number of noise echo photons is set as:
noise trigger probability for a detector triggered by noise->
Comprises the following steps: />
；
In the second period of time, the number of signal echo photons is set to
The number of noise echo photons is->
The detector is triggered with a probability->
Comprises the following steps: />
；
The signal trigger probability is:
；
wherein, when the signal returns the photon number
Is far greater than the number of the echo photons of the noise>
The signal trigger probability is:
；
probability of signal detection
Comprises the following steps: />
；
The probability of noise triggering when the signal comes is
The signal detection probability is->
Time, signal echo photon number->
Comprises the following steps:
；
number of noise echo photons
Comprises the following steps: />
The noise is evenly distributed over time into the detector.
As a further aspect of the invention, the first period of time is of a length
And a second period of time having a length->
The number of noise echo photons in the second period of time->
Comprises the following steps: />
。
The technical scheme provided by the invention has the following beneficial effects:
the invention provides a drift error correction method for satellite laser ranging, which comprises the steps of carrying out signal identification on ground target measurement data by obtaining the satellite ranging data and the ground target measurement data of the same day, and calculating the ground target system delay by combining a nominal value; and counting the number of signal photons and the number of noise photons before the arrival of the signal, calculating the noise triggering probability and the signal detection probability by combining the measurement time, further calculating to obtain the signal triggering probability, and calculating the average ground target echo photon number and the corresponding drift error according to the probability. And adding the calculated earth target drift error and satellite drift error into a result obtained by resolving after signal identification to obtain a corrected result. The satellite laser ranging data is processed by the method, so that the quality of the ranging data can be improved.
The drift error correction method for satellite laser ranging provided by the invention has the advantages that the detection probability and the photon number are transmitted back from the measured data, the drift error corresponding to the photon number is corrected and calculated, the detection information contained in the measured data can be effectively utilized, and the detection information is fed back to the measured data, so that the data quality is improved. The processing result of the measured data shows that the method can effectively improve the data quality.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention. In the drawings:
fig. 1 is a schematic diagram of range gate division and photon distribution in the drift error correction method for satellite laser ranging according to the present invention.
Fig. 2 is a schematic diagram of detection probability distribution of different echo photon numbers in the drift error correction method for satellite laser ranging according to the present invention.
Fig. 3 is a schematic diagram of resolving a relationship (a) between a distance and an average echo photon number and a relationship (b) between a drift error and an average echo photon number in the drift error correction method for satellite laser ranging according to the present invention.
Fig. 4 is a three-stage schematic diagram of a range gate in the drift error correction method for satellite laser ranging according to the present invention.
Fig. 5 is a flowchart illustrating a method for correcting a drift error by using a mathematical model according to the method for correcting a drift error in a satellite laser ranging system of the present invention.
Fig. 6 shows a drift error correction result of satellite ranging data in the drift error correction method for satellite laser ranging according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
The technical solutions in the exemplary embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the exemplary embodiments of the present invention, and it is apparent that the described exemplary embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
The satellite laser ranging has been advancing to a new era of high sensitivity and high precision. The detection device used by most global detection stations is a single photon avalanche diode, has the advantages of high quantum efficiency, high response speed, high sensitivity and the like, and can well meet the requirement of satellite laser ranging. However, variations in the measurement environment, variations in the measurement geometry, and artifacts can cause fluctuations in the laser echo energy that can cause drift errors in the ranging data. Drift errors limit the development of satellite laser ranging to higher accuracy. A satellite laser ranging single photon detection system model is established based on a laser radar detection equation and a detection principle of a single photon detector and combined with a 53cm binocular laser ranging system of a Yunnan astronomical stage of Chinese academy of sciences. And deducing a drift error calculation formula according to the detection model, and calculating drift errors corresponding to different photon numbers. And applying the established model, and providing a drift error correction method combining actual measurement data with a theoretical model. The method is used for processing the ranging data, the rms of the whole section of data can be reduced by 10-100 ps, the drift error caused by energy change in the data is effectively removed, and the data quality is improved.
Specifically, the embodiments of the present invention will be further explained below with reference to the drawings.
Referring to fig. 1, an embodiment of the present invention provides a drift error correction method for satellite laser ranging, which corrects a drift error based on measured data and a theoretical model, and includes the following steps:
acquiring the satellite ranging data and the ground target measurement data of the current day;
performing signal identification on the ground target measurement data, and calculating ground target system delay by combining a nominal value; and counting the number of signal photons and the number of noise photons before the arrival of the signal, calculating the noise triggering probability and the signal detection probability by combining the measurement time, further calculating to obtain the signal triggering probability, and calculating the average echo photon number of the ground target and the corresponding ground target drift error according to the probability.
Adding the calculated system delay into satellite ranging data, performing signal identification on the satellite ranging data, counting the number of signal photons and the number of noise photons before the arrival of a signal, calculating the noise triggering probability and the signal detection probability by combining the measurement time, further calculating the signal triggering probability, and calculating the average echo photon number of the satellite and the corresponding satellite drift error according to the probability.
And adding the ground target drift error and the satellite drift error obtained by calculation into a result obtained by resolving after signal identification to obtain a corrected result.
In this embodiment, a flowchart for correcting the drift error by combining with the theoretical model is shown in fig. 5.
It should be noted that, in the simulation of the single photon detection system, the number of echo photons is calculated,for a single photon detection system, the number of echo photons is a determining factor affecting the detection probability, so the number of echo photons needs to be calculated first. Averaging the number of photons received by the system according to the lidar equation
Comprises the following steps:
in the formula (I), the compound is shown in the specification,
average number of echo photons for a pulse, <' >>
For the energy of each laser pulse>
Based on the number of photons per joule of energy contained in the laser, <' > based on the number of photons per joule of energy>
For the transmittance of the light path of the emission system>
Is the cross-sectional area of the target>
Is a reflection rate of the object and is,
for the effective receiving area of the receiving telescope>
For the optical efficiency of the receiving system>
For the quantum efficiency of the detector>
Is a single passThe atmospheric air transmission rate is greater or less>
For the laser divergence angle, is>
Is the distance between the target and the ranging system>
Is the diameter of the laser-emitted beam. By the formula, the number of echo photons of a specific target under specific system parameters can be calculated.
In the noise rate equation, the noise of the single photon detection system is not negligible for the calculation of the detection probability. The noise mainly consists of two parts, one part is sky light background noise, and the other part is detector dark count noise. Background noise of sky light
The calculation equation of (a) is:
wherein the content of the first and second substances,
the background noise rate, i.e. the number of noise photons received by the detector per unit time,
is the background brightness of daylight and is greater or less than>
For receiving a solid angle of the field of view, <' >>
Is the ratio of the transmission band of the interference filter to the response band of the receiving device>
For the effective receiving area of the receiving telescope>
For the receiving optical efficiency of the receiver>
Quantum efficiency for photoelectric conversion. Is arranged and/or is>
The dark count rate of the detector, the noise sum rate->
Comprises the following steps:
then a specific time period
The number of noise photons is:
for a single photon detector SPAD, a satellite laser ranging station is usually arranged in a Geiger mode when a Geiger mode and a range gate are divided aiming at a single photon detection system detection probability model, namely, an external bias voltage is larger than a reverse breakdown voltage. The working process of the SPAD working under the Geiger mode is as follows: when a photon is detected, the SPAD can generate an avalanche effect, at the moment, the trigger time is recorded by the event timer, the quenching circuit immediately inhibits avalanche, and at the moment, the detector cannot detect; when the avalanche is over, the system restarts to start the next detection. In order to reduce the noise triggering of the detector, a range gate technology is usually added in the detection process. The distance gate technology is realized by the following steps: and calculating the echo time of the signal, and turning on a detector a short time before the echo of the signal to receive the echo signal. Therefore, through time domain filtering, the triggering of noise on the detector can be reduced, and the detection probability of the signal is increased.
Dividing the time into continuous time slots within a range gate time, wherein noise photons exist in each time slot, and noise photons and signal photons exist in the time slot where the signal photons arrive (as shown in fig. 1), so that the photon number of all time slots within the working time of the range gate can be calculated; and because the detector always detects before being triggered, the detection probability of each time slot can be calculated, and a detection probability model is obtained.
For the detection probability model, for SPAD, the probability of photons entering the detector to trigger photoelectrons obeys a poisson distribution, and the formula is as follows:
wherein the content of the first and second substances,
represents in>
To/>
The number of photons entering the detector during this time, in combination with a light signal>
Representing the number of triggered photoelectrons in the time period, based on the measured time period>
Is at>
To>
During which time the detector triggers->
Probability of a single photon. Then in a time from the door, if the detector is at the ^ th>
One time slot is triggered, that requires a preceding
Is not triggered within a time slot.
Since for SPAD, the triggered state is when the number of photoelectrons is not 0, the probability of the detector being triggered is
Is determined, and the probability that the detector is not triggered is then ≥>
The probability of (c). So that the detector is at the fifth->
The probability of a time slot being triggered is:
thus, the triggering probability of the detector in each time slot within a range gate event can be calculated, and a detection probability curve can be obtained; by changing the average echo photon number, the detection probability curves corresponding to different average echo photon numbers can be obtained. The lower graph (fig. 2) shows the probability of detection curves for different mean echo photon counts obtained by simulation.
It can be seen from fig. 2 that when the number of average echo photons is different, the overall trend of the detection probability curve in the time period in which the signal arrives has a shift, and the detection probability changes, that is, the probability peak and the probability distribution of the detected signal photons change.
In a further preferred embodiment of the present invention, in the method for correcting drift error of satellite laser ranging, the method for calculating drift error includes:
setting the actual distance value of the target as
Drift error->
Comprises the following steps:
in the formula (I), the compound is shown in the specification,
is the laser flight distance.
In this embodiment, when analyzing and calculating the distance of the received signal, it is the detection condition of the signal and noise obtained based on the detection probability, and for the target located at a certain specific position, the echo energy fluctuates due to human factors or environmental factors, and usually the distance value corresponding to the distribution of the measurement data fluctuates along with the fluctuation, and these fluctuations will cause the error of the measured distance, that is, the cause of the drift error.
Based on the detection probability model of the single photon detection system, a drift error model can be obtained through calculation.
Therefore, the drift error correction method for satellite laser ranging further includes:
calculating a drift error model based on a detection probability model of the single photon detection system,
resolving laser flight distance based on detection probability
Based on the laser flight distance->
And calculating a weighted average value as a detection probability resolving distance value.
Wherein the detection probability calculates the laser flight distance
The calculation formula of (2) is as follows:
in the formula (I), the compound is shown in the specification,
for the length of the time period during which the signal echo lasts>
Is the probability of detection of the signal within the time period,
the distance value corresponding to each detection probability in the time period. The weighted average value is calculated by the formula and used as a detection probability resolving distance value. />
In a further preferred embodiment of the present invention, in the drift error correction method for satellite laser ranging, for the result of the drift error simulation, the system parameters of a 53cm binocular laser ranging system used for the simulation of the drift error correction method for satellite laser ranging according to the present invention are shown in table 1.
Watch (A)
53cm double-cylinder laser ranging system parameters "
For a 53cm double-tube laser ranging system, the average number of echo photons is of a single photon magnitude, so that 0.1-10 echo photons are subjected to simulation calculation, and the calculated laser flight distance and drift error are shown in fig. 3. Fig. 3 (a) shows a relationship between the calculated distance and the average echo photon number, and fig. 3 (b) shows a relationship between the drift error and the average echo photon number.
As can be seen from (a) and (b) in fig. 3, the echo energy may affect the measurement distance result, thereby causing a drift error in the detection process to vary. When the energy increases, the average echo photon number increases, the measurement distance value becomes smaller, and the drift error of the distance measurement increases. When the average photon number is 0.1, the measurement distance is 488.1086cm, and the drift error is-0.2914 cm; when the average photon number is 10, the measurement distance is 487.4205cm, and the drift error is-0.9795 cm.
Because in the conventional satellite laser ranging process, the earth target measurement result is usually used for correcting the satellite laser ranging result, and the purpose is to correct the system delay which is difficult to directly measure in the ranging process. The method directly subtracts the ground target weighing value from the ground target measurement value to obtain the system delay, so that the satellite measurement data is corrected
Comprises the following steps:
wherein the content of the first and second substances,
for the satellite ranging result, is>
Based on the result of the distance measurement of the ground target>
And weighing the value for the ground target.
However, according to the research of the present invention, it is not possible to exactly match the echo energy of the satellite ranging with the echo energy of the ground target due to the influence of various human or environmental factors during the actual measurement. In order to reduce the drift error caused by echo energy fluctuation, the number of satellite echo photons must be considered
And ground target echo photon number>
The difference in the number of the first and second electrodes. Based on the foregoing analysis, the result of the correction of satellite ranging data is based on when the drift error of the earth target and the satellite is taken into account>
Comprises the following steps:
wherein the content of the first and second substances,
for the satellite ranging result, is>
Based on the result of the distance measurement of the ground target>
Value for the ground target, ->
For a drift error corresponding to the number of photons, <' >>
Is the number of satellite echo photons, <' > is>
Is the number of ground target echo photons.
Therefore, if the average echo photon number of the satellite ranging and the average echo photon number of the earth target measurement are different, the earth target measurement result is used to directly correct the satellite ranging result, which may generate a difference between drift errors, thereby affecting the accuracy of the satellite ranging result.
In a further preferred embodiment of the present invention, it can be seen from the above analysis that in laser ranging, the drift error affects the quality of the ranging data and the ranging accuracy. For drift error, the number of average echo photons is a key factor in determining its size. However, the SPAD cannot directly obtain the average echo photon number, but the detection probability calculation formula includes the average echo photon number, so that the detection probability can be obtained by counting the actual measurement data result, and then the average photon number is calculated according to the detection probability.
According to the principle that the detection probability of the SPAD detector obeys Poisson distribution when the average echo photon number is
When the detector detects->
The probability of an individual photoelectron is:
considering a geiger mode with a range gate, a range gate time is divided into three time periods: before the arrival of the echo signal, within the duration of the echo signal and after the echo signal is finished; as shown in fig. 4, only noise photons enter the detector during the first period and the third period, and both signal photons and noise photons enter the detector during the second period.
In the first period of time, the number of noise echo photons is set as follows:
noise trigger probability for a detector triggered by noise>
Comprises the following steps: />
；
In the second period of time, the number of signal echo photons is set to
The number of noise echo photons is->
The detector is triggered with a probability->
Comprises the following steps: />
；
The signal trigger probability is:
；
wherein, when the signal returns the photon number
Is far greater than the number of the echo photons of the noise>
The signal trigger probability is:
；
probability of signal detection
Comprises the following steps: />
；
The probability of noise triggering when the signal comes is
The signal detection probability is->
Time, signal echo photon number->
Comprises the following steps:
；
number of noise echo photons
Comprises the following steps: />
The noise is evenly distributed over time into the detector.
The first period of time is as follows
And a second period of time having a length->
The number of noise echo photons in the second period of time->
Comprises the following steps:
。
counting the satellite laser ranging result, and then reversely deducing the average echo photon number; with the average number of echo photons, the corresponding drift error can be calculated, and the error term can be corrected, so that the data quality and the precision of satellite laser ranging are improved.
To verify the effectiveness of the proposed method, the measured data is processed with this method. And selecting the ranging data of a 53cm binocular laser ranging telescope of a Yunnan astronomical table in 2019. And (4) correcting the drift error in a segmented mode for each segment of data, calculating rms of the obtained result, and analyzing the obtained result.
Wherein, the data processing and the result. The data adopted during data processing are data obtained by measuring the altitude of the kunming test station by using a 53cm binocular at 18 nights and 1 month in 2019 for the first time through jason2 and kompsat5 and the altitude of the kunming test station by using swarma and jason3 satellites for the second time. In the data processing of each circle, dividing the signals into 10s segments to carry out photon number statistics and calculation and correction of drift errors; when data analysis is carried out, because the distance between the satellite and the observation station is changed at the moment, the calculated distance cannot be directly calculated and judged, and the fitting residual error of the data is calculated. For all divided segments of a circle of data, rms before and after correction of the fitted residual was calculated. Table 2 and fig. 6 show the change in the fitting residual before and after correction.
TABLE 2 Drift error correction results
As can be seen from Table 2, the drift error is processed in a segmented manner, and the rms of the whole data is improved by 10-100 ps, and the improvement is converted into the improvement with the distance from millimeter to centimeter. As can be seen from fig. 6, the data points of the processed fitting residual are more concentrated than the data points before processing, which visually indicates a reduction in the error of the corrected data. Therefore, the satellite laser ranging data processed by the method can improve the quality of the ranging data.
In conclusion, the invention establishes a detection model of a single photon detector in satellite laser ranging, analyzes the cause of drift error in satellite laser ranging and establishes a drift error model. And combining the model with the measured data to provide a drift error correction method combining the measured data with a theoretical model. The method sends back the detection probability and the photon number from the measured data, corrects and calculates the drift error corresponding to the photon number, so that the detection information contained in the measured data can be effectively utilized, and the detection information is fed back to the measured data, so that the data quality is improved. The processing result of the measured data shows that the method can effectively improve the data quality.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A drift error correction method for satellite laser ranging is characterized in that drift errors are corrected by combining measured data with a theoretical model, and the method comprises the following steps:
acquiring satellite ranging data and ground target measurement data;
performing signal recognition on the ground target measurement data, and calculating the ground target average echo photon number and the corresponding ground target drift error according to the ground target signal recognition result;
adding the ground target drift error obtained by calculation into the satellite ranging data, performing signal identification on the satellite ranging data, and calculating the average echo photon number of the satellite and the corresponding satellite drift error according to the satellite signal identification result;
and adding the calculated earth target drift error and satellite drift error into a result obtained by resolving after signal identification to obtain a corrected result.
2. The drift error correction method for satellite laser ranging according to claim 1, wherein the signal recognition is performed on the ground target measurement data, and the ground target average echo photon number and the corresponding ground target drift error are calculated based on the ground target signal recognition result, and the method comprises:
performing signal identification on the ground target measurement data, and calculating ground target system delay by combining a nominal value;
counting the number of signal photons and the number of noise photons before the arrival of the signal, calculating the noise triggering probability and the signal detection probability by combining the measurement time, and further calculating to obtain the signal triggering probability;
and calculating the average echo photon number of the ground target and the corresponding ground target drift error according to the signal triggering probability.
3. The method for drift error correction of satellite laser ranging according to claim 1, wherein the signal recognition of the satellite ranging data and the calculation of the satellite average echo photon number and the corresponding satellite drift error according to the satellite signal recognition result comprise:
performing signal identification on satellite ranging data, and counting the number of signal photons and the number of noise photons before the arrival of a signal;
and calculating the noise triggering probability and the signal detection probability according to the measurement time, further calculating to obtain the signal triggering probability, and calculating the average echo photon number of the satellite and the corresponding satellite drift error according to the signal triggering probability.
4. The drift error correction method for satellite laser ranging according to claim 3, wherein the drift error calculation method for satellite laser ranging includes: setting the actual distance value of the target as
Drift error of
Comprises the following steps:
in the formula (I), the compound is shown in the specification,
is the laser flight distance.
5. The method of drift error correction for satellite laser ranging of claim 4 wherein the laser flight distance
The calculation formula of (2) is as follows:
in the formula (I), the compound is shown in the specification,
for the length of the time period during which the signal echoes last,
is the probability of detection of the signal within the time period,
the distance value corresponding to each detection probability in the time period.
6. The drift error correction method for satellite laser ranging according to claim 4, further comprising:
calculating a drift error model based on a detection probability model of the single photon detection system,
resolving laser flight distance based on detection probability
According to the laser flight distance
And calculating a weighted average value as a detection probability resolving distance value.
7. The method for drift error correction of satellite laser ranging according to claim 6, wherein in the method for drift error correction of satellite laser ranging, the result of correction of satellite ranging data is obtained
Comprises the following steps:
wherein the content of the first and second substances,
as a result of the satellite ranging, it is possible,
for the result of the distance measurement of the ground target,
the value of the ground target is weighed,
in order to correspond to the drift error of the photon number,
for the number of photons that are reflected from the satellite,
is the number of ground target echo photons.
8. The method of claim 7, wherein the calculating the detection probability includes averaging the number of echo photons, obtaining the detection probability by counting the result of the measured data, and calculating the average number of photons according to the detection probability(ii) a Wherein the detection probability follows Poisson distribution when the average echo photon number is
When the detector detects
The probability of an individual photoelectron is:
working in a geiger mode with a range gate, a range gate time is divided into three time periods: before the arrival of the echo signal, within the duration of the echo signal and after the echo signal is finished; in the first period of time and the third period of time, only noise photons enter the detector, and in the second period of time, signal photons and noise photons enter the detector together.
9. The method of claim 8, wherein the number of noise echo photons in the first period of time is:
noise triggering probability of detector triggered by noise
Comprises the following steps:
(ii) a In the second period of time, the number of signal echo photons is set to
The number of noise echo photons is
Probability of detector being triggered in second period
Comprises the following steps:
(ii) a The signal trigger probability is:
(ii) a Wherein, when the signal returns the number of photons
Much larger than the number of noise echo photons
The signal trigger probability is:
(ii) a Probability of signal detection
Comprises the following steps:
(ii) a The probability of noise triggering when the signal comes is
The probability of signal detection is
Time, signal echo photon number
Comprises the following steps:
(ii) a Number of noise echo photons
Comprises the following steps:
the noise is evenly distributed over time into the detector.
10. The method of claim 9, wherein the first period of time is a length of time
The second period of time is
Number of noise echo photons in second period
Comprises the following steps:
。
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